An observational study of centrally facilitated pain in individuals with chronic low back pain

INTRODUCTION: Central pain facilitation can hinder recovery in people with chronic low back pain (CLBP). OBJECTIVES: The objective of this observational study was to investigate whether indices of centrally facilitated pain are associated with pain outcomes in a hospital-based cohort of individuals with CLBP undertaking a pain management programme. METHODS: Participants provided self-report and pain sensitivity data at baseline (n = 97) and again 3 months (n = 87) after a cognitive behavioural therapy–based group intervention including physiotherapy. Indices of centrally facilitated pain were pressure pain detection threshold, temporal summation and conditioned pain modulation at the forearm, Widespread Pain Index (WPI) classified using a body manikin, and a Central Mechanisms Trait (CMT) factor derived from 8 self-reported characteristics of anxiety, depression, neuropathic pain, fatigue, cognitive dysfunction, pain distribution, catastrophizing, and sleep. Pain severity was a composite factor derived from Numerical Rating Scales. Cross-sectional and longitudinal regression models were adjusted for age and sex. RESULTS: Baseline CMT and WPI each was associated with higher pain severity (CMT: r = 0.50, P < 0.001; WPI: r = 0.21, P = 0.04) at baseline and at 3 months (CMT: r = 0.38, P < 0.001; WPI: r = 0.24, P = 0.02). High baseline CMT remained significantly associated with pain at 3 months after additional adjustment for baseline pain (β = 2.45, P = 0.04, R(2) = 0.25, P < 0.0001). Quantitative sensory testing indices of pain hypersensitivity were not significantly associated with pain outcomes at baseline or at 3 months. CONCLUSION: Central mechanisms beyond those captured by quantitative sensory testing are associated with poor CLBP outcome and might be targets for improved therapy.